Argathona rhinoceros

Argathona rhinoceros (Bleeker, 1857)

Restricted synonymy:

Argathona rhinoceros. — Monod, 1976: 853, fig. 1–4.— Bruce, 1982b: 14, fig. 1.— Delaney, 1989: 17, figs 1B, 7, 8.

Argathona rhinocerous. — Anil, Das and Jayaraj, 2018: 297, figs 2–4 [lapsus].

Argathona cf. rhinoceros . — Bruce & Wong, 2015: 160.

Material examined: Female (non-ovig. 15.4 mm), Lazarus Island, 01°13.317′N, 103°51.170′E, 23 May 2013, SCUBA, from Blue-ring Angelfish Pomacanthus annularis, depth, 16.2 m, stn SD 45, SS-0828, coll. Heok Hui Tan & party (ZRC.2022.0014). Female (non-ovig. 13.8 mm), Cyrene Reef, 01°15.374′N, 103°44.816′E, 27 May 2013, hand collected, intertidal, tide at 0.2-1.2 m, stn. IT86, SS-1917, coll. Lee Yen-Ling & party (ZRC.2022.0015). Imm. (c. 13 mm), Kusu Island, 01°13.274′N, 103°51.659′E, 03 Jun 2013, SCUBA, hand collected, depth 19.1 m, stn. SD166, SS-4217, coll. Heok Hui Tan & party (ZRC.2022.0016).

Remarks: Argathona rhinoceros can be recognised by the smooth body surface and prominent rounded rostrum (Monod 1976: 854, figs. 1, 2). This species has been widely reported from fish, primarily groupers. The specimens here were taken from the Blue-ringed Angelfish, Pomacanthus annularis (Bloch). The strong association with fish may be connected to the smooth body surfaces shown by this species, in contrast to many other species in the genus. Photos of this species can be seen at the website “The Biodiversity of Singapore ” at the following link: https://singapore.biodiversity.online/ species/A-Arth-Crus-Isopoda-000098

Fish hosts are Pomacanthus annularis (present work); Lutjanus sp. (as Emperor) (Bruce 1982b); Epinephelus malabaricus (Bloch & Scneider), Epinephelus tauvina (Forsskål), Epinephelus chlorostigma (Valenciennes), Variola louti (Forsskål), Plectropomus leopardus (Lacepède) (all from Delaney, 1989).